The present invention relates to fuel injection pumps of the type having a pump body and distributor rotor in coaxial alignment, the pump body having a pumping chamber provided by an annular arrangement of one or more pumping plunger bores with axes extending generally radially outwardly from the axis of the distributor rotor, a pumping plunger mounted in each plunger bore for reciprocation and annular cam means surrounding the annular arrangement of pumping plunger bores to provide periodic intake and pumping strokes of the plungers for supplying intake charges of fuel to the pumping chamber and delivering high pressure charges of fuel from the pumping chamber for fuel injection, the distributor rotor being rotatably mounted in a distributor head for distributing the high pressure charges of fuel to a plurality of distributor outlets in the distributor head, (such fuel injection pumps being referred to herein as "Rotary Distributor Type Fuel Injection Pumps").
In such Rotary Distributor Type Fuel Injection Pumps, because the fuel charges are delivered at high pressure, the relatively rotating surfaces of the distributor head and distributor rotor are required to have a very precise rotational fit (for example, having a diametral clearance of 80-100 millionths of an inch) to ensure adequate sealing and lubrication. The precise rotational fit presents certain operating problems as follows:
(a) during pump operation, particularly at high speed, a substantial amount of heat is generated by the high pressure fuel charges and by the thin layer of fuel lubricant between the relatively rotating surfaces of the distributor rotor and distributor head; PA1 (b) adequate lubrication of the relatively rotating surfaces is difficult to achieve at high speed and high temperature, particularly with low viscosity fuels such as gasoline and methanol; and PA1 (c) the distributor rotor and distributor head must be maintained at approximately the same temperature throughout the full range of operation of the pump and particularly during cold starting and rapid acceleration; otherwise, the resulting unequal thermal expansion of the parts will cause inadequate lubrication and rotor seizure. PA1 (a) high pressure chamber with small dead volume; PA1 (b) improved valve responsiveness; PA1 (c) low valve wear and long useful valve life; PA1 (d) high electromagnetic actuating force; PA1 (e) precise valve control of the size and timing of the injected fuel charge; PA1 (f) electromagnetic valve operation with a fixed predetermined air gap. PA1 (a) delivery of fuel at a relatively high rate to the pumping chamber during the intake strokes of the pumping plungers; PA1 (b) use of fuel to maintain distributor head and distributor rotor relatively cool and at a relatively constant temperature throughout the full range of operation of the pump; PA1 (c) provision of distributor rotor with a relatively small diameter and coaxial valve member with a relatively large diameter; and PA1 (d) delivery of fuel to the pumping chamber at a relatively low velocity to reduce fuel inertia and minimize cavitation within the high pressure chamber.
A principal aim of the present invention is to provide a new and improved Rotary Distributor Type Fuel Injection Pump which alleviates the above described operating problems presented by the precise rotational fit between the distributor head and distributor rotor.
Another aim of the present invention is to provide a new and improved Rotary Distributor Type Fuel Injection Pump which minimizes or eliminates cavitation within the high pressure chamber of the pump. In accordance with this aim of the present invention, the fuel injection pump employs a new and improved fuel intake system having a relatively large inlet opening and a relatively short inlet passage between the inlet opening and pumping chamber.
Another aim of the present invention is to provide a new and improved Rotary Distributor Type Fuel Injection Pump having a pump body, distributor rotor and electromagnetic control valve which cooperate to provide one or more of the following advantages:
A further aim of the present invention is to provide a new and improved Rotary Distributor Type Fuel Injection Pump having a valve member coaxially mounted within the pump body and distributor rotor to provide one or more of the following advantages:
A further aim of the present invention is to provide in a Rotary Distributor Type Fuel Injection Pump, a new and improved fuel supply system to (a) deliver fuel under pressure to the pumping chamber during the intake strokes; (b) receive fuel spilled from the pumping chamber during the pumping strokes without excessive back pressure; and (c) maintain temperature of distributor rotor and distributor head relatively cool and at a generally constant temperature throughout the full range of operation of the pump.
In accordance with another aim of the present invention, a new and improved Rotary Distributor Type Fuel Injection Pump is provided which (a) can deliver charges of fuel from the high pressure chamber at 12,000 psi and higher; (b) can be used with high speed engines; and (c) can be electrically controlled to precisely regulate the size and timing of the injected fuel charge.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
A better understanding of the invention will be obtained from the following detailed description and accompanying drawings of an illustrative application of the invention.